Hitherto, in the case of forming, e.g., chocolate confectioneries having predetermined shapes by pouring chocolate materials into molds, molds for trial have often been made using, e.g., plastic sheets in predetermined thicknesses. On the other hand, various three-dimensional objects, such as samples and models, have recently been manufactured by 3D printers. In trying to form a prototype that has the same shape as the three-dimensional object with use of a mold, a mold for trial is often made using a plastic sheet in a predetermined thickness by covering a plastic sheet over the three-dimensional object, which has been manufacturing by the 3D printer, and by shaping the plastic sheet with vacuum forming.
As one example of a technique for forming the above-described mold made of the plastic sheet, Patent Document 1 proposes a thermoforming apparatus and a thermoforming method for a plastic sheet. According to the proposed thermoforming apparatus and method, the apparatus includes a press provided with a heat plate for heating a plastic sheet and a forming box arranged movable relative to the press and provided with a sheet holder. The mold made of the plastic sheet is produced by causing the heated plastic sheet to be brought into close contact with a forming die fitted in the forming box that has been moved to a position under the press while a space underside of the forming die is evacuated.